In systems which employ various types of pipe or conduit, it is sometimes necessary to provide either a temporary or permanent closure such pipe or conduit might otherwise be connected, and/or to close openings in fittings or enclosures. Closure means may employ threaded caps or plugs, non-threaded friction fit caps or plugs, soldering, brazing, or welding techniques, and others with which those acquainted with the related arts are familiar. Considering specifically threaded plugs, it will be apparent that some means must be provided for rotating the plug. This may comprise a screwdriver slot, an indented square, or other shape for engagement with a wrench, or an upstanding member such as a square or other shape which may be grasped and turned by means of a suitable tool. Each technique has advantages and disadvantages, depending upon the particular application and size. In commercial wiring, it is frequently necesary to have conduit pass through a concrete barrier such as a foundation or other wall. For convenience, economy and efficiency, it has become standard practice in the art to provide the penetration through the concrete wall by securing a threaded coupling of appropriated length and diameter and supporting the same between the forms which provide the boundary for the poured concrete wall. Unfortunately, it is not always practical to secure a good seal between the coupling and the form comprising a boundary of the concrete wall and therefore, it would be usual for concrete to reach and fill the interior of the coupling. Accordingly, it would be necessary to remove the concrete from the interior of the coupling. It has long been standard practice to prevent entrance of concrete into the coupling by providing a plug at each end thereof. Subsequent to pouring of the wall and removal of the forms, the plugs are removed and appropriate connections made with threaded conduit. It will be immediately apparent that plugs having projecting members for attaching a wrench would not be satisfactory for use in this application because the projecting member would be surrounded with concrete after the wall is poured and it would be necessary to chip away considerable concrete in order to facilitate gaining access to the plug and removal thereof. It might be considered that this difficulty could be overcome by using a coupling of exactly the right length to reach between the forms providing the wall boundary and inserting the plug into the coupling sufficiently far that no part of the plug extends beyond the longitudinal limit of the coupling. However, because a tight fit between the coupling and the concrete form cannot be assured, concrete is almost sure to enter into the void within the coupling and surrounding the upstanding part to which a wrench may be attached. Such concrete will lay in the coupling threads and cause considerable difficulty as an attempt is made to remove the plug and/or to connect threaded conduit. Accordingly, for the application cited, it is customary to use a plug whose upper surface is essentially planar except for an indentation to accomodate a screwdriver, wrench or other turning device. However, there is still a high probability that concrete may enter the indentation making it difficult to use the screwdriver or wrench to turn and remove the plug.
The structure of the present invention has the advantages of the prior art and eliminates, or at least minimizes the difficulties encountered in using prior art devices.
Prior art devices are ubiquitous and may be observed in a wide type of applications and environments. The most typical and ubiquitous prior art devices are illustrated herein in FIGS. 4A, 4B and 4C.
It is an object of the invention to provide a new, improved and economical threaded plug.
It is a more specific object of the invention to provide a threaded plug which has no portion thereof extending above the plane including the upper limit of the threaded body member.
It is another object of the invention to provide a plug of the character described which may be turned by a wide variety of turning tools.
It is another object of the invention to provide a plug of the character described which provides a plurality of means for applying a turning torque.
It is another object of the invention to provide a plug of the character described which can be turned in response to the application of a torque by a lever member.
It is another object of the invention to provide a plug of the character described which provides appropriately positioned and configured surfaces for engagement with and/or by a variety of tools.
It is another object of the invention to provide a plug of the character described which can be readily rotated irrespective of the presence of foreign matter adhering to various portions of the plug.
It is another object of the invention to provide a plug of the character described which can be turned by means of a lever engaged with two appropriately configured and positioned surfaces thereof.
Still another object of the present invention is to provide a new and improved plug for use in the selected applications which substantially overcomes the disadvantages of the described prior art constructions, and which provides a structure characterized by its reliability, ruggedness, ease and convenience of use, simplicity and low cost together with high versitility and adaptability.